The U.S. Pat. No. to Reichl 3,260,548 shows an apparatus for transporting coal from a continuous mining machine in the form of a slurry. In this patent, the slurry is formed in the slurry preparation terminal following the mining machine and is pumped from this terminal to a tank in which the coal is removed from the bottom of the tank and conveyed to a crusher unit where it is again formed into a slurry and pumped from the mine.
U.S. Pat. Nos. 2,528,748; 2,920,635; 2,711,598; 3,690,730 and the British Pat. to Craven No. 599,284 all show various apparatus for transporting coal or other solids in the form of a slurry.
In the apparatus and system of the foregoing patents, it has been difficult to collect and transport solids in the form of a slurry, particularly those mined by continuous mining machines. Such mining machines can mine coal at rates as high as 600 tons per hour and the rate of mining may vary from zero to 600 tons per hour in very short intervals of time. With such a high rate of discharge of the coal, particularly where the fluctuation is as great as encountered in continuous miners, it has been extremely difficult to transport the solids from the machine at the rate of discharge from the machine. This is particularly the case where the machine is operating in low coal seams, where the entire slurry forming equipment must be designed for use in heights of between 5 and 51/2 feet.
The solids discharged from the mining machine, when mixed with water at a solids to water ratio of approximately 30% by weight, result in a slurry of approximately 3500 G.P.M. If the solids could be uniformly fed to form the slurry, the conveying of the solids in the form of a slurry would be no problem, but where the flow of solids from the machine may rapidly fluctuate from zero to 600 tons per hour, it has not been practical to design controls permitting such a solids variation without overflowing the sump or letting the sump go dry at times.
The apparatus of the present invention cures the deficiencies of the prior art patents and slurry conveying systems by obviating the necessity of providing complicated mechanical controls, to take care of high solids fluctuations by providing an inner sump having a high capacity vertical slurry pump in the bottom of the sump and by surrounding the inner sump with an outer sump having side walls substantially higher than those of the inner sump. Both sumps are open at the top, and water is supplied to the inner sump at a constant rate equal to the pump capacity, so the sump level remains substantially constant without any addition of solids. The solids mined by the continuous mining machine are added to the inner sump. At any solids rate above zero, the inner sump will overflow to the outer sump, but the heavy solids and water will be drawn to the main pump and only dirty water and fines will overflow to the outer sump. A pump connected to the outer sump handles the overflow of dirty water and fines.
An advantage of this arrangement is that the removal of the slurry can be controlled without the use of complicated and expensive controls and the overflowing of the inner sump onto the mine floor is completely eliminated.
Another advantage of the present invention is the control of a slurry formed by water discharged into a sump at a constant rate and solids discharged into the sump at a fluctuating rate to eliminate spillage from the inner sump onto the mine floor, caused by the intermittent supply of coal to the slurry formed in the inner sump.
A further advantage of the present invention is the construction and arrangement of a sump permitting a high solids variation without overflowing the sump onto the ground or pumping the sump dry.
A further advantage of the invention is the constructing of a double sump for a vertical slurry pump eliminating the necessity of controls to handle a varying feed rate of solids to the slurry pump.
Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.